Nori under threat from warmer weather

NAGOYA – Climate change is threatening the major central Japan industry of cultivating seaweed for nori, a sector that has been going strong since the late Edo Period.

A steady decline in the harvest of seaweed in shallow waters off the Chita Peninsula in Aichi Prefecture is hurting fishermen and those engaged in making nori, who make up one of the principal industries in the region.

Nori is perhaps best known as a wrapping for sushi.

Its presence on the table for breakfast together with rice, miso soup and green tea was familiar for years in Japan, although since the end of World War II it has ceded ground to bread and coffee or black tea.

Fishermen used to go out to sea all at once between late September and early October to stretch nets attached with spores of seaweed on the surface of the water. The spores matured in 40 days and fishermen harvested nori until spring.

However, the cultivation has undergone a major change as annual production has plunged from more than ¥10 billion in the 1990s to about half that level in recent years.

Construction of Central Japan International Airport, or Centrair, built on an artificial island 35 km south of Nagoya in 2000, caused a great deal of fishing grounds to vanish. Fishermen also were confronted with problems common to traditional domestic industries, including sluggish demand and a shortage of successors.

Now the effect of global warming is endangering the development of seaweed.

Fishermen want seawater to be 23 degrees or less when they spread their nets to grow nori, and recently they’ve had to wait until late October because the water is staying warm longer.

A similar phenomenon is seen in the Ariake Sea surrounded by four prefectures in northwestern Kyushu, shortening the harvest season and reducing the yield.

Global warming may be changing the ecology of some marine creatures.

Striped mullet and opaleye along the coast of Ise Bay in Aichi and Mie prefectures used to move out to open waters in the south during the winter.

But according to the Aichi Fisheries Research Institute, both species may be staying in warmer waters in the bay in winter and feeding on the nori.

Fishermen say migratory ducks flying into Japan for the winter also show up at about the time they lay their nori nets.

Seizo Takeuchi, 71, president of the Onizaki fisheries cooperative in Tokoname, Aichi Prefecture, said ducks ruin all shoots of seaweed, causing tens of millions of yen in damage.

A local fisherman said that development of land for housing means ducks have fewer ponds inland for wintering, so they’ve taken to using coastal areas. He said the increase is also due to people feeding the ducks.

Efforts have been made to scare them away with loud noise or strong lights, but 52-year-old fisherman Hatsuhiko Nakayama of the fishermen’s cooperative said ducks “may flee once, but they soon get used to” the sound and light.

He also said most ducks that eat seaweed are not edible because of their “pungent smell.”